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A ballet dancer spins about a vertical a...

A ballet dancer spins about a vertical axis at `60 "rpm"` with arms outstretched. When her arms are folded the angular frequency increases to `90 "rpm"`. Find the change in her moment of inertia.

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By the principle of conservation of angular momentum `I xx 60 = I_(2) xx 90 `
Final moment of inertia , `I_(2) = (2I)/3`
Change in moment of inertia ` I - (2I)/3 = I/3`
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NARAYNA-SYSTEM OF PARTICLES AND ROTATIONAL MOTION -EXERCISE - IV
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  2. For which of the following does the centre of mass lie outside the bod...

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  3. Which of the following points is the likely position of the cent...

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  4. A particle of mass m is moving in yz - plane with a uniform veloci...

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  5. When a disc rotates with uniform angular velocity, which of the follow...

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  6. A uniform square palte has a small piece Q of an irregular shape...

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  7. In the above problem , the CM of the plate is now in the followin...

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  8. The density of a non-uniform rod of length 1m is given by rho (x) = a ...

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  9. A Merry -go-round, made of a ring-like plarfrom of radius R and mass M...

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  10. Choose the correct alternative :

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  11. Figure shows two identical particles 1 and 2 , each of mass m ...

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  12. The net external torque on a system of particles about an axis is zero...

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  14. A uniform uniform sphere of mass m and radius R is placed on a ro...

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  15. A T shaped object with dimesions shown in the figure , is lying a...

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  16. A circular ring of mass 6kg and radius a is placed such that its cente...

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  17. In the figure d shown a hole of radius 2 cm is made in a semicir...

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  18. The figure shows the positions and velocities of two particles . ...

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  19. A rod of length 3m and its mass par unit length is directly propo...

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  20. A wheel is rotating about an axis through its centre at 720 rp...

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  21. A particle of mass m describes a circle of radius r . The centripetal ...

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